We hope to gain greater understanding of the regulation of cholesterol metabolism. Our immediate goals are to isolate variants of cultured cells which are resistant to the potent competitive inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, ML-236B (Compactin). We will characterize the cholesterol metabolism of these cells and expect to find that resistance is attained by overproduction of the target enzyme. Enzyme prepared from cells which greatly overproduce HMG-CoA reductase will be used as antigens for the production of monoclonal antibodies to reductase. The antibodies will then be used to determine the mechanism of enzyme overproduction and to examine the physiological mechanisms of regulation such as suppression by Low Density Lipoprotein (LDL). The availability of cells that produce HMG-CoA reductase as a major percentage of total cellular protein and the availability of anti-reductase antibody will eventually permit a study of the mechanism of regulation of reductase at the gene level.